Should/must not: ~아/어서는 안 되다, ~(으)면 안 되다

Here you will learn how to use ~아/어서는 안 되다 which means "you shouldn't" and ~(으)면 안 되다 which also means "you shouldn't". 

You can learn more about 되다 specifically in Learning Passive Voice in Korean.

If you want to say that something is not going well or has not been completed, you should use the word 안. 

To complete the sentence in this grammar, you can insert "잘" before "안". Besides being able to be used together with "안" "못" can also be used instead. 

Example:

> 저는 시험을 (잘) 못 봤어요

   I didn't do (well) in this test.

> 그의 옷은 아직 세탁 안 되요

   His clothes still haven't been washed

> 여기서 컴퓨터가 (잘) 안 돼요 

   The computer is not working properly here

There are many circumstances where you'll hear Koreans say "안 되다," one of which is a situation where you're not ready to do something, or when something isn't going well. You can also often hear it at the end of a grammar rule with a completely different meaning.

You can't/ You shouldn't: ~아/어서는 안 되다 

You can probably understand how a new grammar principle works just by looking at the title. This one is pretty easy to understand. Adding ~아/어서는 안 되다 at the end of a sentence will result in a meaning that means 'should not'. The sentence that comes right before this grammatical is always in the present tense.

For examples:

> 너무 늦게 자서는 안 됩니다

   You shouldn't stay up too late

> 공부에 게으러서는 안 됩니다

   You shouldn't be lazy with your studies

Although these sentences are always in the present tense, the activity being referred to usually happened in the past (unless you are just saying in general that you "shouldn't" do something). For example:

> 그렇게 불을 피우서는 안 됩니다

   Don't start a fire like that

Shortly before the sentence is uttered, one might run too fast which causes one to utter the sentence "그렇게 불을 피우서는 안돼요."

Must not : ~(으)면 안 되다

By adding ~(으)면 안 되다 to the end of a sentence or phrase, you can create a sentence that means "You should not ..... ". This meaning is very similar to the meaning learned above (~아/어서는 안 되다), but the meaning will be a bit stronger if we use ~(으)면 안 되다. Some examples:

> 그렇게 먹으면 안 돼요

   You must not eat it like that

> 그런 농담을 하면 안 돼요 

   You must not make jokes like that

One thing to note about this grammar principle is that it is often used in the form of a question. For example:

> 이렇게 하면 안 돼요? 

   Can't you do it like this?

> 더 빨리 하면 안 돼요? 

   Can't you go any faster?

If you want to say it with a more polite level, you can use "아/어 주다". In fact, "아/어 주다" (or just 주다). For example:

> 접시 좀 주면 안 돼요?

   Can you get me some plates?

> 시럽 몇 병만 주면 안돼요?

   Can you give me a few bottles of syrup?

That's all for today's lesson. If you have any questions, please feel free to contact me through social media. Thank you for visiting my page. Have a nice day :)